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AIAA Aviation Conference!Washington, D.C.!June 13-17, 2016!
Inlet Trade Study for a Low-Boom Aircraft Demonstrator!
National Aeronautics and Space Administration
Christopher M. Heath & John W. Slater!NASA GRC – Cleveland, OH!Sriram K. Rallabhandi!
National Institute of Aerospace – Hampton, VA!
https://ntrs.nasa.gov/search.jsp?R=20170002621 2020-06-08T11:17:03+00:00Z
Research Motivation!
Overland sonic boom challenges supersonic aircraft viability.!
Current State-of-the-Art: !• Adjoint-based shape optimization to match low-boom signature!• Isolated inlet, engine core, nozzle design and subsequent integration!Drawbacks: !• Low-boom optimization neglects propulsion effects, sacrifices inlet/airframe performance &
TSFC to meet low-boom objective!• Research shows introducing propulsion effects into a pre-optimized airframe pressure
signature can compromise low-boom performance !
Propagated Ground Signature*
(a) Nozzle/plume Mach contours for full-deck configuration. ↵ = 0.875
(b) Nozzle/plume Mach contours for cropped-deck configuration. ↵ = 1.0
50 75 100 125 150 175Distance along sensor, ft
-0.005
-0.0025
0
0.0025
0.005
Δp/
p ∞
TargetFull-deckCropped-deck
(c) Near-field pressures for full- and cropped-deck configura-tions, with optimization target as reference. h/L = 3
0 20 40 60 80 100 120Time, ms
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
Pres
sure
cha
nge,
psf
Target, 71.5 PLdBFull-deck, 74.7 PLdBCropped-deck, 79.5 PLdB
(d) Predicted ground signature from 50,000 ft cruise altitude,with target signature as reference
Figure 12. Powered simulation results for full- and cropped-deck configurations using linear nozzle geometry
at cruise thrust condition. Each adaptively refined mesh contains 100 M cells. Cruise altitude is 50,000 ft,
M1 = 1.5, Tcruise
= 4, 200 lb
13 of 24
American Institute of Aeronautics and Astronautics
Compromised Boom
Performance
Unpowered Target
Powered
Near%Field%
Mid%Field%
Far%Field%
Far%Field%
*Wintzer, M. et. al., AIAA Paper No. 2015-1045.! 2
3-‐D CFD
1-‐D Burgers’
Eq.
Research Objectives!
1. Quantify installation effects on inlet/engine performance. !2. Quantify installation effects on airframe/sonic boom performance.!
Approach: !Compare isolated vs. installed performance of two inlet types on aerodynamically tailored low-boom reference* airframe.!
Axisymmetric Spike Inlet Streamline-‐Traced Inlet
*Ref. vehicle designed w/Euler adjoint-based shape optimization to achieve under-track loudness <76.4 PLdB. Wintzer, M. et. al., AIAA Paper No. 2015-1045.!
3
Government Ref. !Vehicle – Config. 25D Spike STEX
Problem Definition – Single Pt. Design!
Reference Cruise Pt. !§ 55K-ft std. day alt.!§ Mach no. = 1.6!§ CL= 0.065, α ≈ 3.25°!§ 21K lb cruise weight!!
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Estimated Reference !GE-F404-402 Conditions!
Inlet!§ W2 = 51.2-lbm/s!§ Pt,2 = 6.1-psi!§ Tt,2 = 590-deg R!!Nozzle!§ W6 = 52.6-lbm/s!§ Pt,6 = 21.4-psi!§ Tt,6 = 2852-deg R!!§ TSFC = 1.53-lbm/lbf-hr!§ Fnet = 4487-lbf!
Government Ref. !Vehicle
Solution Overview!
Freestream(
Supersonic(ou0low(
Symmetry(
Riemann(invariants(
Subsonic(inflow(
Subsonic(ou0low(
1. Near-‐field Domain
!"#"$"%&:! !
!! − !!,!"#$%!!!
!"#$%&'!!":! !0 < ! < 5!
−1 < δA! < 1!!"#ℎ!!ℎ!":! !
!!"# = !!"# !!
2. Compute Performance
3. OpLmizaLon Problem
Nozzle Throat Area
Angle of APack
5
4. Compute Sonic Boom
Process & Tools!
6
ComputaLonal Steps
1. Parameterize airframe geometry (ESP).!
2. Design & size custom inlets (SUPIN).!
3. Integrate inlet/airframe geometry (ESP).!
4. Discretize surface geometry (Pointwise).!
5. Discretize volume w/plume sourcing (AFLR3).!
6. Compute RANS vehicle performance (Fun3D).!
7. Compute inlet rec. & adjust ref. engine cycle. (NPSS)!
8. Balance vehicle forces using adjoint-based optimization (Fun3D/SNOPT).!
9. Generate sonic boom grid (Inflate).!
10. Perform sonic boom RANS analysis (Fun3D).!
11. Extrapolate mid-field signatures to ground and convert to perceived loudness (sBOOM).!
Inlet Performance Comparison!
! Supercritical! Critical! Subcritical!
Spike!
! ! !
STEX!
!
! !! ! !"#ℎ!#! ! !
Figure!10:!Mach!number!contours!for!isolated!inlets!at!the!symmetry!plane.!
!! Supercritical! Critical! Subcritical!
Spike!
! ! !
STEX!
! ! !! ! !"#ℎ!#! ! !
Figure!12:!Mach!number!contours!for!installed!inlets!at!the!symmetry!plane.!! Supercritical! Critical! Subcritical!
Spike!
! ! !
STEX!
! ! !!
! !!,!/!!,!!!!
Figure!13:!Total!pressure!recovery!contours!for!installed!inlets!at!the!AIP.!
!
0.91%
0.92%
0.93%
0.94%
0.95%
0.96%
0.97%
0.75% 0.80% 0.85% 0.90% 0.95% 1.00% 1.05%
Pressure&Recovery&
W2/WIdeal&
Characteris7c&Cane&Curves&&(Isolated&&&Installed)&
Spike%(Isolated)%STEX%(Isolated)%Spike%(Installed)%STEX%(Installed)%
Similar isolated/installed characteristics!!Installed Spike !
• Peak recovery declines by ~1%!• ~1% reduction in mass flow rate!!
Installed STEX !• Peak recovery declines by ~1.5%!• ~2% reduction in mass flow rate!
1%
1.5%
7 Mach #!
Isolated!
Installed!
Shock/BL interaction
Inlet Performance Comparison @ AIP!
! Supercritical! Critical! Subcritical!
Spike!
! ! !
STEX!
! ! !! ! !!,!/!!,!!!
!!
Figure!11:!Total!pressure!recovery!contours!for!isolated!inlets!at!the!AIP.!
!
! Supercritical! Critical! Subcritical!
Spike!
! ! !
STEX!
! ! !! ! !"#ℎ!#! ! !
Figure!12:!Mach!number!contours!for!installed!inlets!at!the!symmetry!plane.!! Supercritical! Critical! Subcritical!
Spike!
! ! !STEX!
! ! !!
! !!,!/!!,!!!!
Figure!13:!Total!pressure!recovery!contours!for!installed!inlets!at!the!AIP.!
!
Parameter! STEX! Spike!Pt,2 /Pt,0 ! 0.94! 0.97!DPC/P ! 0.0408! 0.0075! DPR/P ! 0.086! 0.028!
• Installed spike inlet recovery ~3% higher than STEX recovery!
• Both inlets meet SAE ARP radial & circumferential distortion requirements for GE-F404-402!
• Spike inlet fan distortion at AIP is significantly lower than STEX inlet distortion!
8
Isolated!
Installed!
Low!Momentum
Pt,2 /Pt,0 !
Vehicle Performance Comparison!
Parameter! Spike! STEX!α (°) ! 3.26! 3.23!
Airframe L/D ! 4.75! 4.94!Dnet (lbf) ! 4391! 4230!
TSFC (lbm/lbf-hr) ! 1.452! 1.416!Range! -! +6.6%!
!"#!" = ! !!"#$
!! !"
!!!!
!STEX
Spike High pressure on
spike nacelle !
High pressure on wing trailing edge!
Low pressure on STEX nacelle !
9 Cp!
!!
Vehicle Sonic Boom Comparison!
! !
! !!
!"#ℎ!#!!
!
Figure'16.'Mach'characteristics'for'spike'(Left)'and'STEX'(Right)'configurations'at'the'symmetry'plane.'RANS'computations'on'viscous'core'and'collar'meshes.'
!
Compression!feature!from!inlet!nacelle!!
• Mach-aligned extruded prism grid generated using Inflate out to 6 body lengths!
10
Spike STEX Mid-Field Sonic Boom Grid!
• Pressure signals!extracted from !h/L = 1-5 at!Φ = 0°-50°!
h/L = 1 (1 Body Length)
h/L = 2 (2 Body Lengths)
Mach #!
-0.006!
-0.004!
-0.002!
0.000!
0.002!
0.004!
10.0! 15.0! 20.0! 25.0! 30.0! 35.0! 40.0! 45.0! 50.0!
ΔP/
P!
X(m)!
Near-Field Pressure Waveforms!
Spike!STEX!
Mid-Field Pressure Waveform Comparison!
-0.008!
-0.006!
-0.004!
-0.002!
0.000!
0.002!
0.004!
0.006!
0.0! 10.0! 20.0! 30.0! 40.0! 50.0!
ΔP/
P!
X(m)!
Near-Field Pressure Waveforms (Spike)!
Φ = 0!Φ = 10!Φ = 20!Φ = 30!Φ = 40!Φ = 50!
-0.008!
-0.006!
-0.004!
-0.002!
0.000!
0.002!
0.004!
0.006!
0.0! 10.0! 20.0! 30.0! 40.0! 50.0!
ΔP/
P!
X(m)!
Near-Field Pressure Waveforms (STEX)!
Φ = 0!Φ = 10!Φ = 20!Φ = 30!Φ = 40!Φ = 50!
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Inlet nacelle compression
Strong aW compression Φ = 0
h/L = 5
Peak magnitudes increase w/Φ
Peak magnitudes increase w/Φ
Strong peak compression
Strong peak expansion
h/L = 5
h/L = 5 Under-track
Off-track
-0.3!
-0.2!
-0.1!
0.0!
0.1!
0.2!
0.3!
0.4!
0.5!
0! 20! 40! 60! 80! 100! 120! 140! 160!
Pres
sure
Cha
nge
(psf
) !
Time (ms)!
Predicted Ground Signatures (STEX)!
Φ = 0, 82.58 PLdB!Φ = 10, 82.97 PLdB!Φ = 20, 82.29 PLdB!Φ = 30, 81.25 PLdB!Φ = 40, 78.99 PLdB!Φ = 50, 72.54 PLdB!
-0.3!
-0.2!
-0.1!
0.0!
0.1!
0.2!
0.3!
0.4!
0.5!
0! 20! 40! 60! 80! 100! 120! 140! 160!
Pres
sure
Cha
nge
(psf
) !
Time (ms)!
Predicted Ground Signatures (Spike)!
Φ = 0, 81.77 PLdB!Φ = 10, 81.10 PLdB!Φ = 20, 80.54 PLdB!Φ = 30, 80.80 PLdB!Φ = 40, 78.63 PLdB!Φ = 50, 72.34 PLdB!
Vehicle Propagated Ground Signature Comparison!
!!
12
• Under-track loudness higher than original design (~82 vs. 76.4 PLdB)!
• Differing engine geometry!• Euler vs. RANS (viscous effects)!• Re-adjusted α to hit target CL!
• Adjoint-adapted grids vs. geometry refined!
• Improvement to sonic boom performance likely recoverable with additional RANS aerodynamic shaping!
Loudness decreases w/Φ
Loudness decreases w/Φ
Conclusions!
Ø Inlet trade study conducted to capture effects of engine installation on inlet performance!
Ø Simultaneously captured the effects of engine installation on aircraft performance AND sonic boom!
13
Conclusions!
Spike inlet configuration:!Ø ~3% higher total pressure recovery!Ø >70% lower inlet distortion!Ø ~1% lower propagated ground loudness!!STEX inlet configuration:!Ø Lower external wave drag (~160-lbf)!Ø ~4% higher vehicle L/D ratio!Ø ~2.5% lower TSFC!Ø +6.6% increased range capability!
14
Conclusions!
Ø Integration of a “low-boom” inlet does not automatically guarantee reduction in overall vehicle sonic boom signature.!
!Ø Inlet interaction with the vehicle signature plays a
much more dominant role. !!Ø Inlet integration should be considered during the
conceptual vehicle design optimization process.!
15
Acknowledgements!
!NASA’s Commercial Supersonic Technology (CST) Project!!Jon Seidel – Thermodynamic cycle support!Chuck Trefny – Propulsion-airframe integration!Bob Haimes – SUPIN and ESP software integration!John Dannenhoffer – ESP custom parameterizations!
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